Recently, in facsimile machines, a memory transmission (store-and-forward) technique is popularly used. According to the memory transmission techniques, image data related to a document which is read is compressed and temporarily stored in a memory, and the image data which is read out from the memory depending on the reception capability of the destination facsimile machine is compressed again and transmitted. The memory is also used in a memory reception to store the received image data in an available memory region when the paper runs out during an automatic reception, for example.
According to the conventional memory reception, the line density is set to 15.4 lines/mm, 7.7 lines/mm, 3.85 lines/mm and the like from a panel on the transmitting facsimile machine. At the receiving facsimile machine, a predetermined line density is applied to all pages of the received document if the predetermined line density is set during an initial procedure of the automatic reception. Conventionally, there exists no procedure for changing the predetermined line density which is set during the reception of the document.
Next, a description will be given of an example of a conventional facsimile machine, by referring to FIGS.1 and 2. FIG. 1 shows a conventional facsimile machine 1, and FIG. 2 shows an operation sequence of the facsimile machine 1.
In FIG. 1, the facsimile machine 1 generally includes a main control part (CPU) 10, an operation control part 11, a recording part 12, a reading part 13, a compression/restoration part 14, a memory 15, and a communication control part 20. An operation panel 11-1 is connected to the operation control part 11, and the communication control part 20 is made up of a modem 16 and a line control part 17.
Under the control of the main control part 10, each function such as the line density is set from the operation panel 11-1 which is connected to the operation control part 11. In addition, the dialing of the destination number is made from the ten-key, a one-touch key or the like of the operation panel 11-1. When the line is connected, the pre-procedure shown in FIG. 2 is started when the destination facsimile machine has the automatic reception function.
On the other hand, the reading part 13 optically reads the inserted document and outputs the image data related to the read document. This image data is coded in the compression/restoration part 14 according to the modified Huffman (MH) coding, for example, under the control of the main control part 10, and is thereafter stored temporarily in the memory 15.
When the transmission mode is set in the modem 16 within the communication control part 20 by the pre-procedure, the image data is read out from the memory 15 under the control of the main control part 10. The read out image data is restored in the compression/restoration part 14 before being compressed again depending on the transmission mode. The image data which is compressed again is modulated in the modem 16 and is transmitted to a line L via the line control part 17.
The image data which is received from the line L is supplied to the modem 16 via the line control part 17 and is demodulated in the modem 16. The demodulated image data is temporarily stored in the memory 15 in the compressed form under the control of the main control part 10 or, is restored in the compression/restoration part 14 and printed on a recording paper by the recording part 12.
In FIG. 2, the destination number is dialed from the transmitting facsimile machine (hereinafter simply referred to as the transmitting side) and a calling signal (CNG) is transmitted to the receiving facsimile machine (hereinafter simply referred to as the receiving side). An accepted answer (CED) is returned from the receiving side, and the capability notification of the facsimile pre-procedure is made by notifying signals (NSF, DIS). In other words, the notification of capabilities such as the transmission speed (for example, 9600 bps, 4800 bps, 2400 bps) of the receiving side is made, and the transmitting side specifies the line density to 15.4 lines/mm, for example, by a transmission command (NSS), and at the same time, transmits a synchronizing training signal (TDF). If an answer (CFR) is received from the receiving side in response to the above, the transmitting side transmits the image (Pix) with the specified line density of 15.4 lines/mm. After an end of procedure (EOP) indicating the end of transmission of all of the pages is transmitted from the transmitting side, the transmitting side confirms an answer (MCF) from the receiving side and transmits a disconnect request (DCN).
Therefore, according to the conventional facsimile machine, the same line density is applied during the pre-procedure before the transmission of the image data and also during the after-procedure, and the line density cannot be switched during the procedure.
For example, when the receiving side starts the automatic reception or the paper runs out during the automatic reception, the operation mode is automatically switched to the memory reception mode. However, particularly in the case of a compact type facsimile machine, the memory capacity is set relatively small in order to reduce the cost of the machine. For this reason, there are problems in that the quantity of data the image data which is received may exceed the memory capacity and the memory reception of all of the image data may not be possible. Particularly when the line density is set to a large density such as 15.4 lines/mm from the transmitting side, the image data quantity is large and the possibility of the data quantity exceeding the memory capacity is high. In addition, the amount of paper which may be accommodated within the compact type facsimile machine is limited, and the compact type facsimile machine runs out of paper more frequently compared to the facsimile machines of larger sizes.